Lightweight dash insulator construction

ABSTRACT

A sound insulating component includes a decoupling layer disposed under a cap layer comprising a thermoplastic cellular foam. Advantageously, the cap layer has sufficient rigidity to maintain a predetermined shape and has an airflow resistance that allows a predetermined amount of airflow through the sound insulating component. In another embodiment, a hybrid sound insulating component includes a cap layer and a decoupling layer with an airflow control layer interposed thereof. A method of making the sound control components is also provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention provides in at least one embodiment a light weight sound insulation component, in particular, the present invention provides a light weight dash insulator.

2. Background Art

Reduction of noise propagation into automobile passenger compartments is becoming an important design consideration, as cabin quietness is assuming an increasing role in vehicle manufacturers' marketing plans. A significant and growing portion of the automotive NVH (Noise, Vibration, Harshness) materials market is migrating from mass-based acoustical composites to light weight constructions that do not rely on heavy mass barriers. Light weight constructions are usually multi-layered composites that acoustically perform as well as, if not better than, barrier products at generally lower costs and at a fraction of the weight. Weight reduction is becoming more critical in the automotive industry as fuel costs have recently skyrocketed and more CAFÉ restrictions (i.e., higher gas mileage mandates) are widely anticipated.

Many prior art sound reduction components utilize configurations comprised of a barrier layer adjacent to a decoupling layer. In these configurations, the barrier layers block sound by reflection while decoupling layers provide some sound dissipative function (i.e., sound absorbing). Moreover, in many of these prior art barrier-decoupling configurations, vehicle barrier weight ranges from a minimum of 0.5 pound per square foot to an average of about 1.50 pound per square foot. This converts for a typical dash insulator to part barrier weights in the 10 to 30 pounds range. Some light weight prior art sound reduction components are based on multi-layer constructions of thermoplastic layers with inclusion of additional layer(s), usually referred to as airflow control layers, whose function is to regulate overall airflow throughout the composite. This function is critical as airflow resistivity, or airflow resistance values, correlate with material NVH performance, such as transmission or insertion loss, normal or random sound absorption, as well as vehicle-specific performance such as noise reduction.

U.S. Pat. No. 6,145,617 (the '617 patent) discloses the use of a thin stiff cap layer made from compressed resinated cotton fiber and a decoupler layer. In other prior art construction, a cap layer and a non-woven, vertically lapped decoupling layer are used in conjunction with an impermeable film layer. In this latter configuration, the airflow control layer is interposed between the cap layer and a vertically lapped decoupling layer and heated to adhere both layers. Although this prior art configuration works reasonably well, lower weights and cost reductions are still highly desirable.

Accordingly, there is a need for improved, lightweight automotive noise abatement components that effectively reduce noise levels in the vehicle passenger compartment.

SUMMARY OF THE INVENTION

The present invention solves one or more problems of the prior art by providing in at least one embodiment a sound insulating component. The sound insulating component of this embodiment is lightweight while providing excellent sound insulation properties in automotive applications. The sound insulating component of this embodiment includes a decoupling layer disposed below a cap layer comprising a thermoplastic cellular foam. In addition, the cap layer has sufficient rigidity to maintain a predetermined shape and has airflow resistance values that allow a predetermined amount of airflow through the sound insulating component.

In another variation of the present invention, a hybrid sound insulating component is provided. The sound insulating component of this embodiment includes a cap layer and a decoupling layer with an airflow control layer interposed thereof. The airflow control layer allows additional adjustment of the airflow resistance of the sound insulating component as compared to the first embodiment. As such, it provides additional sound transmission loss properties as compared to the first embodiment, thereby yielding a more balanced blend of absorption and transmission loss.

In still another embodiment of the present invention, a method of making the sound insulating components set forth above is provided. The method of this embodiment includes a step in which a sheet of a thermoplastic cellular foam is molded to a sheet of a sound absorbing material to form the sound insulating component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-section of an embodiment of the present invention;

FIG. 2 is a schematic cross-section of another embodiment of the present invention that includes an airflow control layer;

FIG. 3A is a schematic illustration of an apparatus used to form the sound insulating components of the invention in which component sheets are heated during molding; and

FIG. 3B is a schematic illustration of an apparatus used to form the sound insulating components of the invention in which component sheets are heated prior to molding.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Reference will now be made in detail to presently preferred compositions or embodiments and methods of the invention, which constitute the best modes of practicing the invention presently known to the inventors.

With reference to FIG. 1, an embodiment of the sound insulating component of the present invention is provided. Sound insulating component 10 includes cap layer 12 and decoupling layer 14. Decoupling layer 14 is disposed between the vehicle sheet metal 16 and the cap layer 12. In one variation, sound insulating component 10 has an airflow resistance from about 400 MKS rayls to 4500 MKS rayls. In another variation, sound insulating component 10 has an airflow resistance from 500 MKS rayls to 3000 MKS rayls. In yet another variation, sound insulating component 10 has an airflow resistance from about 1,200 MKS rayls to 1,800 MKS rayls. In still another variation, sound insulating component 10 has an airflow resistance greater than 2500 MKS rayls. In a refinement of this latter variation, sound insulating component 10 has an airflow resistance from 3000 MKS rayls to 4500 MKS rayls. Sound insulating component 10 may be virtually any thickness compatible with the intended sound insulation application. Typically, sound insulation component 10 varies in thickness from 0.12 inches to 2.0 inches.

Cap layer 12 comprises a thermoplastic cellular foam which has a sufficient airflow resistance to allow a predetermined amount of airflow through insulating component 10. In one variation of the present embodiment, cap layer 12 has an airflow resistance from 300 MKS rayls to 4500 MKS rayls. In another variation, cap layer 12 has an airflow resistance from 500 MKS rayls to 2500 MKS rayls. In still another variation, cap layer 12 has an airflow resistance greater than 2500 MKS rayls. In a refinement of this latter variation, cap layer 12 has an airflow resistance from 3000 MKS rayls to 4500 MKS rayls. Typically, cap layer 12 has a thickness from 0.04 inches to 0.5 inches after molding. In one useful variation, cap layer 12 acts by both absorbing and reflecting incident sound waves. In some variations, the amount of sound absorption is greater than the amount of sound reflection. In other variations, the amount of sound reflection is greater than the amount of sound absorption.

In another variation of the present embodiment, cap layer 12 has a sufficient rigidity to maintain a predetermined shape. The ability of maintaining a predetermined shape allows sound insulating component 10 to conform to the shape of vehicle component 16 which may have flat or curved surface 18. Typically, cap layer 12 has a shear modulus from 0.1 MPa to 1.5 MPa Suitable thermoplastic cellular foams from which cap layer 12 are formed include open cell foams. Specific examples of materials from which the thermoplastic cellular foams are formed include, but are not limited to, foams selected from the group consisting of polyurethane (“PUR”), expandable polystyrene (“EPS”), expandable polypropylene (“EPP”), expandable polyethylene (“EPE”), and combinations thereof. In one variation, the thermoplastic cellular foam has a volume density ranging from 1.0 to 4.0 lbs/ft3.

Sound insulating component 10 advantageously has a lower weight than many of the analogous prior art sound insulating constructions. To this end, in one variation, cap layer 12 has a surface density that is less than or equal to about 0.055 lb/ft2. In one variation, cap layer 12 has a surface density that ranges from 0.03 lb/ft2 to 0.055 lb/ft2. It should also be appreciated that when cap layer 12 contacts decoupling layer 14, the thermoplastic nature of cap layer 12 assists in adhering these layers together. This adhesion is accomplished during the heating process in which sound insulating component 10 is formed (see below).

Decoupling layer 14 comprises a sound absorbing material. Useful materials for forming decoupling layer 14 include the prior art materials used to form decoupling layers. Examples of such materials include the materials disclosed in U.S. Pat. No. 6,145,617 (the '617 patent) for the porous resilient layer. The entire disclosure of this patent is hereby incorporated by reference. In one variation, decoupling layer 14 includes a moldable thermoplastic foam. For example, the moldable thermoplastic foam can have a density from 1.0 to 3.5 lbs/ft3. In another variation, decoupling layer 14 is formed from thermoplastic fiber material. Specific materials from which decoupling layer 14 may be formed include, but are not limited to, polyurethane sheet or molded foams, PET, PET/cotton blends, polypropylene, polypropylene/PET fiber blends, non-woven vertically lapped PET or PET-cotton blend, and combinations thereof. Typically, decoupling layer 14 has a thickness from about 0.08 inches to about 1.5 inches (after molding). Decoupling layer 14 typically has a surface density from about 0.08 lb/ft2 to about 0.3 lb/ft2 and an airflow resistance from about 100 MKS rayls to about 500 MKS rayls.

Still referring to FIG. 1, sound insulating component 10 is advantageously used to provide sound insulation in an automobile. Therefore, in a variation of the present embodiment, sound insulating component 10 is adjacent to vehicle component 16. In this variation, decoupling layer 14 is positioned adjacent to flat or curved surface 18. FIG. 1 shows the sound insulating component 10 utilized as a dash insulator, however, examples of other applications of component 10 include, but are not limited to, the sound insulation of wheelhouse covers, quarter trim panels, engine side, vehicle floor pan, trunk components, doors and side coverings. Sound insulating component 10 is particularly useful for dash insulator applications.

With reference to FIG. 2, another embodiment of the present embodiment is provided. Hybrid sound insulating component 30 includes airflow control layer 32 disposed between decoupler layer 14 and cap layer 12. The details of the appropriate materials and physical specifications of cap layer 12 and decoupling layer 14 are the same as those set forth above in connection with the description of FIG. 1. Airflow control layer 32 is particularly useful in allowing further tuning of the airflow resistance of hybrid sound insulating component 30 and thus the NVH performance of the material. In a variation of the present embodiment, airflow control layer 32 has an airflow resistance from 300 MKS rayls to 4500 MKS rayls. In another variation, airflow control layer 32 has an airflow resistance greater than 4500 MKS rayls. In this latter variation, airflow control layer 32 acts as a barrier predominately reflecting incident sound waves. Suitable materials from which airflow control layer 32 is formed include thermoplastic polymers such as polyethylene and polypropylene, and combination thereof. FIG. 2 shows the sound insulating component 30 utilized as a dash insulator, however, examples of other applications of component 30 include, but are not limited to, the sound insulation of wheelhouse covers, quarter trim panels, engine side, vehicle floor pan, trunk components, doors and side coverings. Sound insulating component 30 is particularly useful as a hybrid dash insulator applications.

In still another embodiment, a method of forming the sound insulating component described above is provided. With reference to FIGS. 3A and 3B variations of the present embodiment are schematically illustrated. FIG. 3A provides a schematic illustration of a first variation in which heating is provided during molding while FIG. 3B provides a schematic illustration in which heating is provided prior to molding. The methods of the present embodiment each independently comprise a step in which sheet 50 of a thermoplastic cellular foam is molded to sheet 52 of a sound absorbing material to form sound insulating component 10. Sheet 50 of thermoplastic cellular foam forms cap layer 12 while sheet 52 of sound absorbing material forms decoupling layer 14 as set forth in connection to the descriptions of FIGS. 1 and 2. As illustrated in FIG. 3A, sheets 50, 52 are provided from rolls 56, 58 into heated molding tool 80 mounted in molding press 60. Heated mold 80 applies heat to sheets 50, 52 to form the sheets into the final shape of molded sound insulating component 10. In another variation, molding tool 80 is heated electrically or by hot oil. Subsequently, after removal from molding tool 80, the parts are cooled and trimmed. In one variation, sheets 50, 52 are present in heated molding tool 80 for about 30 to 60 seconds. As illustrated in FIG. 3B, sheets 50, 52 are provided from rollers 56, 58 into oven 64 which applies heat to sheets 50, 52. Oven 64 may use conventional oven heating technology (e.g. infra-red, convection, or contact heating) to accomplish the heating. Heated sheets 50, 52 are then provided to water-cooled molding tool 90 located in molding press 66 to form molded sound insulating component 10 with the predetermined final shape. Again, after removal from molding tool 90 the parts are trimmed. When an airflow control layer is used as in the embodiment described in connection with FIG. 2, sheet 70 provided from roller 72 is interposed between sheets 50, 52 prior to heating. In each of these variations, sheet 50 typically has a thickness from 0.08 inches to 0.5 inches before molding resulting in cap layer 12 having a thickness of 0.04 inches to 0.5 inches after molding. Similarly, decoupling layer 14 typically has a thickness up to about 2.0 inches before molding resulting in a thickness from about 0.08 inches to about 1.5 inches after molding.

While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. 

1. A sound insulating component comprising: a cap layer comprising a thermoplastic cellular foam, the cap layer having sufficient rigidity to maintain a predetermined shape and having an airflow resistance that allows a predetermined amount of airflow through the sound insulating component; and a decoupling layer disposed between the vehicle sheet metal and the cap layer, the decoupling layer comprising a sound absorbing material.
 2. The sound insulating component of claim 1 wherein the thermoplastic cellular foam is an open cell foam.
 3. The sound insulating component of claim 1 wherein the thermoplastic cellular foam comprises a plastic selected from the group consisting of polyurethane, expandable polystyrene, expandable polypropylene, expandable polyethylene, and combinations thereof.
 4. The sound insulating component of claim 1 wherein the thermoplastic cellular foam has a volume density from 1.0 to 4.0 lbs/ft3.
 5. The sound insulating component of claim 1 having a surface density less than or equal to 0.055 lb/ft2.
 6. The sound insulating component of claim 1 wherein the cap layer has a thickness from 0.04 inches to 0.5 inches.
 7. The sound insulating component of claim 1 having an airflow resistance from 400 MKS rayls to 4500 MKS rayls.
 8. The sound insulating component of claim 1 having an airflow resistance from 500 MKS rayls to 3000 MKS rayls.
 9. The sound insulating component of claim 1 having an airflow resistance greater than MKS 2500 rayls.
 10. The sound insulating component of claim 5 having an airflow resistance from 3000 MKS rayls to MKS 4500 rayls.
 11. The sound insulating component of claim 1 wherein the cap layer has a shear modulus from 0.1 MPa to 1.5 MPa
 12. The sound insulating component of claim 1 wherein the decoupling layer comprises a moldable thermoplastic foam.
 13. The sound insulating component of claim 12 wherein the moldable thermoplastic foam has a density from 1.0 to 4.0 lbs/ft3.
 14. The sound insulating component of claim 12 wherein the decoupling layer comprises a component selected from the group consisting of a polyurethane molded or sheet foam, a non-woven vertically lapped PET or PET-cotton fiber blend, and combinations thereof.
 15. The sound insulating component of claim 12 wherein the vehicle component is selected from the group consisting of dash insulators, wheelhouse covers, quarter trim panels, engine side, vehicle floor pan, trunk components, doors and side coverings.
 16. A sound insulating component comprising: a cap layer comprising a thermoplastic cellular foam, the cap layer having sufficient rigidity to maintain a predetermined shape and having an airflow resistance that allows a predetermined amount of airflow through the sound insulating component; an airflow control layer disposed between the cap layer and the decoupler layer providing the sound insulating component with a predetermined airflow resistance; and a decoupling layer, the decoupling layer comprising a sound absorbing material.
 17. The sound insulating component of claim 16 wherein the airflow control layer has an airflow resistance from 300 MKS rayls to 4500 MKS rayls.
 18. The sound insulating component of claim 17 configured as a hybrid dash insulator.
 19. A method of forming a sound insulating component comprising a cap layer comprising a thermoplastic cellular foam, the cap layer having sufficient rigidity to maintain a predetermined shape and having an airflow resistance that allows a predetermined amount of airflow through the sound insulating component; and a decoupling layer disposed below the cap layer, the decoupling layer comprising a sound absorbing material, the method comprising: a) molding a sheet of a thermoplastic cellular foam to a sheet of a sound absorbing material to form the sound insulating component wherein the sheet of thermoplastic cellular foam forms the cap layer and the sheet of sound absorbing material forms the decoupling layer.
 20. The method of claim 19 wherein the sheet of a thermoplastic cellular foam and the sheet of a sound absorbing material are heated prior to or during step a). 